Aerodynamic roughness length related to non-aggregated tillage ridges

Wind erosion in agricultural soils is dependent, in part, on the aerodynamic roughness length (z0) produced by tillage ridges. Although previous studies have related z0 to ridge characteristics (ridge height ( RH) and spacing (RS)), these relationships have not been tested for tillage ridges ob- served in the North African agricultural fields. In these re- gions, due to climate and soil conditions, small plowing tools are largely used. Most of these tools produce non-aggregated and closely-spaced small ridges. Thus, experiments were conducted in a 7-m long wind tunnel to measure z0 for 11 ridge types covering the range of geometric characteristics frequently observed in south Tunisia. Experimental results suggest that RH 2 /RS is the first order parameter controlling z0. A strong relationship between z0 and RH 2 /RS is proposed